/**
 * @file STL_MD5.cpp
 * @author Derek Liu (yjkhtddx@sina.com)
 * @brief 
 * @version 0.1
 * @date 2020-09-10
 * 
 * @copyright Copyright Sci-Tech Laboratories (c) 2020
 * 
 */

/* interface header */
#include "STL_MD5.h"

/* system implementation headers */
#include <stdio.h>
#include <string.h>

// Constants for MD5Transform routine.
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

///////////////////////////////////////////////

namespace STL
{

  // F, G, H and I are basic MD5 functions.
  inline MD5::uint4 MD5::F(uint4 x, uint4 y, uint4 z)
  {
    return (x & y) | (~x & z);
  }

  inline MD5::uint4 MD5::G(uint4 x, uint4 y, uint4 z)
  {
    return (x & z) | (y & ~z);
  }

  inline MD5::uint4 MD5::H(uint4 x, uint4 y, uint4 z)
  {
    return x ^ y ^ z;
  }

  inline MD5::uint4 MD5::I(uint4 x, uint4 y, uint4 z)
  {
    return y ^ (x | ~z);
  }

  // rotate_left rotates x left n bits.
  inline MD5::uint4 MD5::rotate_left(uint4 x, int n)
  {
    return (x << n) | (x >> (32 - n));
  }

  // FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
  // Rotation is separate from addition to prevent recomputation.
  inline void MD5::FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
  {
    a = rotate_left(a + F(b, c, d) + x + ac, s) + b;
  }

  inline void MD5::GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
  {
    a = rotate_left(a + G(b, c, d) + x + ac, s) + b;
  }

  inline void MD5::HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
  {
    a = rotate_left(a + H(b, c, d) + x + ac, s) + b;
  }

  inline void MD5::II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac)
  {
    a = rotate_left(a + I(b, c, d) + x + ac, s) + b;
  }

  //////////////////////////////////////////////

  // default ctor, just initailize
  MD5::MD5()
  {
    init();
  }

  //////////////////////////////////////////////

  // nifty shortcut ctor, compute MD5 for string and finalize it right away
  MD5::MD5(const std::string &text)
  {
    init();
    update(text.c_str(), text.length());
    finalize();
  }

  //////////////////////////////

  void MD5::init()
  {
    finalized = false;

    count[0] = 0;
    count[1] = 0;

    // load magic initialization constants.
    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;
  }

  //////////////////////////////

  // decodes input (unsigned char) into output (uint4). Assumes len is a multiple of 4.
  void MD5::decode(uint4 output[], const uint1 input[], size_type len)
  {
    for (unsigned int i = 0, j = 0; j < len; i++, j += 4)
      output[i] = ((uint4)input[j]) | (((uint4)input[j + 1]) << 8) |
                  (((uint4)input[j + 2]) << 16) | (((uint4)input[j + 3]) << 24);
  }

  //////////////////////////////

  // encodes input (uint4) into output (unsigned char). Assumes len is
  // a multiple of 4.
  void MD5::encode(uint1 output[], const uint4 input[], size_type len)
  {
    for (size_type i = 0, j = 0; j < len; i++, j += 4)
    {
      output[j] = input[i] & 0xff;
      output[j + 1] = (input[i] >> 8) & 0xff;
      output[j + 2] = (input[i] >> 16) & 0xff;
      output[j + 3] = (input[i] >> 24) & 0xff;
    }
  }

  //////////////////////////////

  // apply MD5 algo on a block
  void MD5::transform(const uint1 block[blocksize])
  {
    uint4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    decode(x, block, blocksize);

    /* Round 1 */
    FF(a, b, c, d, x[0], S11, 0xd76aa478);  /* 1 */
    FF(d, a, b, c, x[1], S12, 0xe8c7b756);  /* 2 */
    FF(c, d, a, b, x[2], S13, 0x242070db);  /* 3 */
    FF(b, c, d, a, x[3], S14, 0xc1bdceee);  /* 4 */
    FF(a, b, c, d, x[4], S11, 0xf57c0faf);  /* 5 */
    FF(d, a, b, c, x[5], S12, 0x4787c62a);  /* 6 */
    FF(c, d, a, b, x[6], S13, 0xa8304613);  /* 7 */
    FF(b, c, d, a, x[7], S14, 0xfd469501);  /* 8 */
    FF(a, b, c, d, x[8], S11, 0x698098d8);  /* 9 */
    FF(d, a, b, c, x[9], S12, 0x8b44f7af);  /* 10 */
    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

    /* Round 2 */
    GG(a, b, c, d, x[1], S21, 0xf61e2562);  /* 17 */
    GG(d, a, b, c, x[6], S22, 0xc040b340);  /* 18 */
    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[0], S24, 0xe9b6c7aa);  /* 20 */
    GG(a, b, c, d, x[5], S21, 0xd62f105d);  /* 21 */
    GG(d, a, b, c, x[10], S22, 0x2441453);  /* 22 */
    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[4], S24, 0xe7d3fbc8);  /* 24 */
    GG(a, b, c, d, x[9], S21, 0x21e1cde6);  /* 25 */
    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
    GG(c, d, a, b, x[3], S23, 0xf4d50d87);  /* 27 */
    GG(b, c, d, a, x[8], S24, 0x455a14ed);  /* 28 */
    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[2], S22, 0xfcefa3f8);  /* 30 */
    GG(c, d, a, b, x[7], S23, 0x676f02d9);  /* 31 */
    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    HH(a, b, c, d, x[5], S31, 0xfffa3942);  /* 33 */
    HH(d, a, b, c, x[8], S32, 0x8771f681);  /* 34 */
    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[1], S31, 0xa4beea44);  /* 37 */
    HH(d, a, b, c, x[4], S32, 0x4bdecfa9);  /* 38 */
    HH(c, d, a, b, x[7], S33, 0xf6bb4b60);  /* 39 */
    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[0], S32, 0xeaa127fa);  /* 42 */
    HH(c, d, a, b, x[3], S33, 0xd4ef3085);  /* 43 */
    HH(b, c, d, a, x[6], S34, 0x4881d05);   /* 44 */
    HH(a, b, c, d, x[9], S31, 0xd9d4d039);  /* 45 */
    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[2], S34, 0xc4ac5665);  /* 48 */

    /* Round 4 */
    II(a, b, c, d, x[0], S41, 0xf4292244);  /* 49 */
    II(d, a, b, c, x[7], S42, 0x432aff97);  /* 50 */
    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[5], S44, 0xfc93a039);  /* 52 */
    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
    II(d, a, b, c, x[3], S42, 0x8f0ccc92);  /* 54 */
    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[1], S44, 0x85845dd1);  /* 56 */
    II(a, b, c, d, x[8], S41, 0x6fa87e4f);  /* 57 */
    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[6], S43, 0xa3014314);  /* 59 */
    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[4], S41, 0xf7537e82);  /* 61 */
    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[2], S43, 0x2ad7d2bb);  /* 63 */
    II(b, c, d, a, x[9], S44, 0xeb86d391);  /* 64 */

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;

    // Zeroize sensitive information.
    memset(x, 0, sizeof x);
  }

  //////////////////////////////

  // MD5 block update operation. Continues an MD5 message-digest
  // operation, processing another message block
  void MD5::update(const unsigned char input[], size_type length)
  {
    // compute number of bytes mod 64
    size_type index = count[0] / 8 % blocksize;

    // Update number of bits
    if ((count[0] += (length << 3)) < (length << 3))
      count[1]++;
    count[1] += (length >> 29);

    // number of bytes we need to fill in buffer
    size_type firstpart = 64 - index;

    size_type i;

    // transform as many times as possible.
    if (length >= firstpart)
    {
      // fill buffer first, transform
      memcpy(&buffer[index], input, firstpart);
      transform(buffer);

      // transform chunks of blocksize (64 bytes)
      for (i = firstpart; i + blocksize <= length; i += blocksize)
        transform(&input[i]);

      index = 0;
    }
    else
      i = 0;

    // buffer remaining input
    memcpy(&buffer[index], &input[i], length - i);
  }

  //////////////////////////////

  // for convenience provide a verson with signed char
  void MD5::update(const char input[], size_type length)
  {
    update((const unsigned char *)input, length);
  }

  //////////////////////////////

  // MD5 finalization. Ends an MD5 message-digest operation, writing the
  // the message digest and zeroizing the context.
  MD5 &MD5::finalize()
  {
    static unsigned char padding[64] = {
        0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

    if (!finalized)
    {
      // Save number of bits
      unsigned char bits[8];
      encode(bits, count, 8);

      // pad out to 56 mod 64.
      size_type index = count[0] / 8 % 64;
      size_type padLen = (index < 56) ? (56 - index) : (120 - index);
      update(padding, padLen);

      // Append length (before padding)
      update(bits, 8);

      // Store state in digest
      encode(digest, state, 16);

      // Zeroize sensitive information.
      memset(buffer, 0, sizeof buffer);
      memset(count, 0, sizeof count);

      finalized = true;
    }

    return *this;
  }

  //////////////////////////////

  // return hex representation of digest as string
  std::string MD5::hexdigest() const
  {
    return hexLowerDigest();
  }

  std::string MD5::hexUpperDigest() const
  {
    if (!finalized)
      return "";

    char buf[33];
    for (int i = 0; i < 16; i++)
      sprintf(buf + i * 2, "%02X", digest[i]);
    buf[32] = 0;

    return std::string(buf);
  }

  std::string MD5::hexLowerDigest() const
  {
    if (!finalized)
      return "";

    char buf[33];
    for (int i = 0; i < 16; i++)
      sprintf(buf + i * 2, "%02x", digest[i]);
    buf[32] = 0;

    return std::string(buf);
  }

  std::string MD5::binaryDigest() const
  {
    if (!finalized)
      return "";
    return std::string((char *)digest,16);
  }

  //////////////////////////////

  std::ostream &operator<<(std::ostream &out, MD5 md5)
  {
    return out << md5.hexdigest();
  }

  //////////////////////////////

  std::string md5(const std::string str)
  {
    MD5 md5 = MD5(str);
    return md5.hexdigest();
  }

  std::string md5_upper(const std::string str)
  {
    MD5 md5 = MD5(str);
    return md5.hexUpperDigest();
  }
  std::string md5_lower(const std::string str)
  {
    MD5 md5 = MD5(str);
    return md5.hexLowerDigest();
  }

  std::string md5_binary(const std::string str)
  {
    MD5 md5 = MD5(str);
    return md5.binaryDigest();
  }
} // namespace STL